1. Field of the Invention
The present invention relates to a technique for supplying fuel to an internal combustion engine.
2. Description of the Related Art
There has been known a fuel supply device which separates a raw fuel and generate a fuel having characteristics different from the raw fuel, and which supplies these fuels. As such fuel supply device, for example, there is a device equipped with a separator which separates a raw fuel into a high octane number fuel having higher octane number than the raw fuel and a low octane number fuel having lower octane number than the raw fuel (refer to Japanese Patent Application Laid-Open No. 2007-231818, and Japanese Patent Application Laid-Open No. 2004-522039).
Performance of separating the fuel (transmission rate) depends on a temperature of the separator, so that adjustment of the temperature of the separator becomes one of important problems of the fuel supply device. On this point, there is proposed a device which adjusts the temperature of the separator, by heating the fuel as a separation target beforehand (refer to Japanese Patent Application Laid-Open No. 2004-232624). Further, there is proposed a device which performs temperature raising of the separator rapidly, by injecting the high octane number fuel having high evaporation temperature into the separator, so as to adjust the temperature rapidly at the starting of the engine (refer to Japanese Patent Application Laid-Open No. 2010-144735). Further, there is proposed a device which raises the temperature of the separator favorably, by increasing a pressure of a raw fuel supplied to the separator, in the case where the temperature of the separator is low (refer to Japanese Patent Application Laid-Open No. 2010-1754).
However, there is a problem that, even when the fuel or the separator is heated beforehand, the temperature of the separator drops from an evaporative latent heat or a radiation of the fuel generated during separation, and that a raw fuel separation performance of the separator cannot be maintained to a desired manner.